Core drill



Oct. I23, 1934. ;l H. HQWARD Er AL 1,978,085

CORE DRILL Filed Jan. 16, 1935 3 sheets-sheet 1 Z6 j/ .96 36 36 39 a5/5' 40 .37

79 93 :s Je a9 se a/ 9/ 97 .7m/enfers 33 `lh/7 H. Howard Oct. 23, 1934.H HOWARD ET AL 1,978,085

coRE DRILL Filed Jan. 16, 1933 3 Sheets-Sheet 2 3\ 39 47 p25 lf 37 "'4643 36 36 5/ 45 40 9 -47 42 45 /50 IY: l @f 68 5.3 6/ 34 35 .F295 Si@ E97X 33 59 66 76 los 56 36 7260 77 6555 I ,l 4/ 3 1=f 55 f77 Ven/'ors@ffy-MM Oct. 23, 1934.

J. H. HOWARD ET AL CORE DRILL Filed Jan. 16, 1953 3 Sheets-Sheet 3 J'o/mH. Howard /l/frea' C. Caf/ama Patented oci. z3, 1934 UNITED STATESPATEN'l; OFFICE John H. Howard,

Catland, Alhambra, Oil Tools Co., of California CORE DRILL HuntingtonPark, and Alfred C. Calif., assignors to Globo Los Nietos, Calif., acorporation `This invention relates to a well tool, and relates It is ageneral more particularly to a core drill.

object of the present invention to provide an improved core drillinvolving simple, practical and dependable cutter mounting means.

Another object of the invention is to provide a simple and effectivemeans for detachably mounting rotatable cutters on a well drilling tool.

Another object of the invention is a Well tool including cutterassemblies mounted in the bit head of the tool in a manner so that toprovide they may be easily and quickly removed or replaced at the welldrilling rig.

cannot be loosened during the drilling operations, or have any of theirparts lost in the well bore.

Another object of the invention is to provide a core drill bit headhaving recesses for holding the cutters and cutter mounting means thateffectively rotatably support the cutters in the recesses and securelyconnect or tie together the portions of the bit head at the oppositeends of the recesses.

Another object of the invention is to provide a practical and dependablemeans for detachably mounting rotatable cutters on a well tool that issuch that the cutters may be accurately and correctly positioned andmounted on the bit head of the tool without using special tools orequipment.

Another object of the invention is to provide a cutter mounting of thecharacter mentioned including a two-piece bearing, each piece or part ofthe bearing having portions of dilerent diameters providing shouldersthat cooperate with oppositely faced internal shoulders in the rotatablecutter to eiectively support the cutter against end thrusts in bothdirections.

It is another object of the invention to provide a. cutter `mountinginvolving a practical and effective bearing for rotatably supportingthat consists of two integrally connected parts.`

A further object of the invention vide a cutter mounting of thecharacter mentioned that includes a bearng that directly rotatablycarries the cutter and that may be treated to be wear resistant,` and apin or bolt that carries the bearing that is not subjected to any wearor friction so that it may be treated for maximum toughness.

A further object of the invention is to provide a core drill havingsimple and eifectlve means for handling the circulation fluid for flcutters.

the cutter is to proushngthe A further object of the invention is toprovide a simple and inexpensive core drill bit head body or shoe forcarrying a plurality of rotatable cutters.

-Various objects and features of the invention will be best and fullyunderstood from the following detailed description of typical preferredforms and applications of the invention, throughout which descriptionreference is made to the accompanying drawings, in which:

Fig. 1 is a side elevation of a core drill involving one form of theinvention with certain parts broken away to appear in vertical crosssection. Fig. 2 is an enlarged vertical detailed sectional view of thebit head and cutter assemblies of the tool illustrated in Fig. 1, beinga -view taken as indicated by line 2-2 on Fig. 3. Fig. 3 is a bottomview of the bit head and cutter assemblies. Fig. 4 is an enlargedvertical detailed sectional view of the bit head body or shoe, being aview taken as indicated by line 4-4 on Fig. 5. Fig. 5 is a bottom viewof the bit head shoe. Fig. 6 is an enlarged end view of one of thecutter assemblies apart from the other portions of the tool. Fig. 7 is alongitudinal detailed sectional view of the several parts of one of thecutter assemblies. Fig. 8 is an end view of the pin or bolt embodied inthe cutter assembly.l Fig, 9 is a fragmentary vertical detailedsectional view of the tool embodying a cylindrical cutter carried by thecutter mounting means provided by the invention. Fig. 10 is afragmentary vertical detailed sectional view of a tool including a.frusta-conical inner cutter with its small end irmermost and carried bythe mounting means of the invention. Fig. 11 is an enlarged end view ofone of the parts of a bearing included in the cutter assembly. Fig. 12is a side elevation of the bearing part illustrated in Fig. 11. Fig. 13is an end view of another part of the bearing, and Fig. 14 is a sideelevation of the bearing part illustrated in Fig. 13.

The bit head structure and the detachable cutter assemblies provided bythe present invention may be embodied in coring outfits or core drillsof various types. Our co-pending application entitled Rock core drill,Serial No. 727,499, illed May 25, 1934, describes and claims a structureof the same general class as that of the present invention. Throughoutthe following detailed description, we will disclose typical preferredforms of the invention embodied in a more or less common form of coringoutt or core drill, it being understood that the invention is not t0 betaken as limited or restricted to the specific forms or applicationsabout to be described, but is to be taken as including any features ormodifications that may fall within the scope of the claims.

The core drill illustrated in Fig. 1 of the drawings includes generally,a body or outer barrel 10, an inner barrel 11 for receiving the core, abit head 12 on the lower end of the outer barrel 10, and a plurality ofreplaceable cutter assemblies 13 and 14 on the bit head 12.

The outer barrel 10 of the core drill is an elon gate tubular structureadapted to be connected with the lower end of an operating string ofdrill pipe, or the like. In the particular case illustrated in thedrawings, a sub l5 having a tapered screw-threaded pin 16 is provided onthe upper end of the outer barrel 10 to facilitate connection of thebarrel with the operating string. A sub or connecting .member 17 isscrew-threaded on the lower end of theouter barrel 10 and is providedwith a downwardly projecting pin 18. A bit head sub 19 is provided onthe lower end of the connecting member 17 to carry the bit head 12. Thesub 19 is a tubular member having a central longitudinal opening 20. Thesub 19 has comparatively heavy or thick walls, and a screwthreadedsocket 21 is provided in its lower end. A threaded socket 22 is providedin the upper end of the bit head sub 19 to receive or cooperate with thepin 18 of the connecting member 17.

The inner barrel l1 is arranged within the outer barrel 10 to receivethe core. The core receiving barrel 11 is a tubular structure, and isprovided at its lower end with an enlarged portion 23 screw-threadedinto the opening 20 of the bit head sub 19. The inner barrel 11 is ofconsiderably less diameter than the outer barrel 10 so that an annularfluid passage 24 is provided between the two barrels. A suitable vent orvalve may be provided on the upper end of the core barrel 1l to permitthe escape of fluid or air from the inner barrel as the core enters thebarrel and to prevent the flow of circulation fluid into the upper endof the inner barrel. In the particular structure illustrated in thedrawings, a valve body 25 is provided in the upper end of the innerbarrel 1l and has a reduced opening with a valve seat (not shown). Theball 26 is adapted to cooperate with the valve seat of the body 25 toclose the upper end of the inner barrel 11 against the entrance ofcirculation i'luid. A cage 27 is provided to hold or maintain the wallvalve 26 in its proper position.

The bit head 12 is attached to the lower end of the sub 19 and isprovided to carry the removable cutter assemblies 13 and 14. The bithead 12 includes a body or shoe 28. The shoe 28 is an annular or tubularmember and as illustrated in the drawings, may be integral. The bit headshoe 28 has a threaded connection with the sub 19. In the specificconstruction illustrated in the drawings, a pin 29 is provided on theupper end of the bit head shoe 28 to screw-thread into the socket 21. Ashoulder 30 may be provided on the shoe 28 at the base of the pin 29 tocooperate with the lower end of the sub 19. The vertical or longitudinalopening 31 in the shoe 28 is in vertical alignment with the opening inthe sub 19 and barrel 11, and its lower end is of reduced diameter. Adownwardly and outwardly inclined annular face 32 is provided on thelower end of the shoe 28 at the lower end of the opening 31. Inaccordance with the invention, outwardly projecting enlargements orwings 33 are provided on the shoe 28. The wings 33 are preferablyequally spaced apart around the exterior ot the shoe 28 and are of equalwidth or thickness. 'Ihe sides 34 of the wings 33 may be flat andvertical and the opposite sides of each wing may be substantiallyparallel. The spaces between the several wings 33 form longitudinal orvertical grooves 35 in the exterior of the shoe 28 to permit the upwardflow of circulation fluid from the bottom of the well bore.

Recesses are provided in the shoe 28 of the blt head to receive or carrythe cutter assemblies 13 and 14. The recesses are provided in the lowerend of the shoe 28 at the outwardly projecting wings 33. The number ofwings 33 provided on the bit head and the number and shape of therecesses in the bit head depend upon the respective number of cutterunits 13 and 14 embodied in the tool. In the particular form of theinvention being described, there are two substantially diametricallyopposite pairs of cutter assemblies 13 provided on the bit head, andrecesses 36 are provided in the lower end of the shoe 28 at two pairs ofadjacent wings 33. The tool also includes two cutter units 14 carried inrecesses 37 in the lower end of the shoe 28 at diametrically oppositewings 33.

The cutter assemblies 13 include outer cutters for acting on theformation at the bottom of the well bore and for reaming or cutting thewell bore to size, while the cutter assemblies 14 include inner cuttersfor acting on the formation at the bottom of the bore and for shaping ortrimming the core. The recesses 36 for receiving the outer cutter units13 extend upwardly in the shoe 28 from its lower end and have upwardlyand inwardly inclined inner and outer walls 38. The upper walls 39 ofthe recesses 36 may be inclined downwardly and inwardly. Each recess 36extends substantially tangentially through the bit head from one side ofa wing 33 to the other. Radial slots 40 extend upwardly from the lowerend of the shoe 28 and intersect the lower end portions of the recesses36. The slots 40 have flat parallel side walls at substantially rightangles to the inner and outer walls 38 of the recesses 36. The slots 40are enlarged throughout portions of their lengths by round bores 41 and42. The axes of the bores 41 and 42 are aligned and are inclinedupwardly and outwardly, being at substantially right angles to the innerand outer walls of the recesses 36. As the bores 41 and 42 extendlongitudinally or radially through the slots 40, they are in the natureof rounded depressions in the opposite vertical walls of the slots. Thebores 41 which are provided in the slots 40 adjacent the inner walls ofthe recesses 36 are of larger diameter than the bores 42 which areprovided in the slots adjacent the outer walls of the recesses 36.Counter bores 43 are provided in the other sides of the wings 33 to jointhe bores 42. The counter bores 43 are coaxial with the bores 41 and 42and accordingly have inclined axes. Counter bores 44 are provided in thewalls of the shoe opening 31 to join the inner bores 41. The counterbores 44 are coaxial with the bores 4l and 42 and are somewhat smallerin diameter than the outer counter bores 43.

The recesses 37 for carrying the, inner cutter assemblies 14 extendupwardly into the lower end of the bit head shoe 28 at diametricallyopposite wings 33. The inner and outer side walls 45 of the recesses 37are inclined downwardly and inwardly relative to the vertical axis ofthe tool. The upper walls 46 of the recesses 37 may incline downwardlyand outwardly as illustrated in Fig.

4 of the drawings. Vertical slots 47 extend upwardly into the lower endof the shoe 28 and intersect the lower end portions of the recees 37.The slots 47 are radial relative to the longitudinal axis of the shoeand have vertical parallel walls.

Bores 48 and 49 areprovided in the walls of the slots 47. The bores 48and 49 extend longitudinally or radially through the slots 49 and havealigned upwardly and inwardly inclined axes. The bores 49 are providedin the walls of the slots 47 at the inner walls of the recesses 37,while the bores 48 communicate with the recesses 37 at their outerwalls. The bores 48 are larger in diameter than the bores 49. Counterbores 50 are provided in the outer lower corners of the wings 33 to jointhe outer ends of the bores 48. Counter bores 51 are provided in thewalls of the shoe opening 31 to join the inner bores 49. The counterbores 50 and 51 have upwardly and inwardly inclined axes aligned withthe axes of the bores 48 and 49.

I'he cutter assemblies 13 and 14 are removably locked or mounted in therecesses of the blt head shoe 28 and their cutters are operable to makean annular cut in the earth formation. The outer cutter assemblies 13each includes a rotatable cutter 53, a bearing 54 for directly rotatablycarrying the cutter 53 and a pin or bolt 55 for removably holding thebearing 54 in position. In the form of the invention illustrated in thedrawings,

the cutters 53 of the outer cutter assemblies are' rotatable on inclinedaxes and are in the nature of frustro-conical cutters. Longitudinallyextending peripheral cutting parts or teeth 56 are provided on thecutters 53. The opposite ends of the cutters 53 are preferably flat andnormal to the cutters axes of rotation. When the cutters 53 arerotatably mounted-within the recesses 36, they project from the lowerends of the shoe 28 to engage the formation at the bottom of the wellbore and their lower cutting edges are substantially horizontal. 'I'heouter ends of the cutting teeth 56 may be bevelled as at 58 so that thecutters are effective in acting on the side walls of the well bore. Acentral longitudinal opening 59 is provided in each cutter 53. Inaccordance with the invention, enlargements or sockets are provided inopposite ends of the openings 59 to provide oppositely facing annularshoulders in th openings. The sockets 60 in the outer ends of the cutteropenings 59 are of round cross section and their bottoms or inner endsform outwardly facing annular shoulders 61. The shoulders 61 may beinclined or tapered inwardly. The sockets 62 in the inner ends of thecutter openings 59 are somewhat smaller in diameter than the sockets 60and their inner ends form inwardly facing annular shoulders 63 in thecutter openings. The shoulders 63 may be inclined inwardly asillustrated throughout the drawings.

The bearings 54 directly rotatably support the outer cutters 53 and haveparts cooperating with the slots which hold them against rotation. It isa feature of the invention that the bearings 54 are operable to transmitend thrusts in either direction directly from the cutters 53 to the shoe28. In accordance with the invention, each bearing 54-is formed oftwoparts, an inner part 64 and an outer part 65. The inner parts 64 ofthe bearings fit the inner end sockets 62 of the cutters 53. The innerbearing parts 64 have outwardly extending continuations or extensions 66of reduced diameter that project through the cutter openings 59. Annularinclined shoulders 67 are provided at the bases or inner ends of theextensions 66 'and are adapted to cooperate with the shoulders 63 in thecutter openings. The

youter ends 68 ot the bearing parts 64 are flat, and are adapted to seatagainst or cooperate with the inner walls of the recesses 36.Diametrically opposite lugs 69 are provided on theends 68 to cooperatewith the slots 40 at the inner walls of the recesses 36. The lugs 69have ilat parallel sides to cooperate with the ilat walls of the slots40. A central longitudinal opening 70 extends through each bearing part64 and is provided at its outer end with a socket or enlargement 71.

The outer parts 65 of the bearings 54 ilt or are carried in the sockets60 in the outer ends of the cutters 53. The outer bearing parts 65 havetaperedinner ends 72 for cooperating with the shoulders 61 in the cutteropenings. The outer ends 73 of the bearing parts 65 are adapted toengage the outer walls of the recesses 36. Central longitudinal openings74 are provided in the bearing parts 65 and have enlargements or sockets75 in their inner ends adapted to receive the end portions of theextensions 66 of the bearing parts 64. 'I'he bottoms of the sockets 75provide shoulders 76 for cooperating with the ends oi. the extensions66.

When the two parts 64 and 65 of the bearings are assembled in thecutters, the extensions 66 of the inner parts extend into the sockets 75and their ends seat against the shoulders 76. In accordance with theinvention, the two parts 64 and 65 of each bearing are integrallyconnected or joined after the two bearing parts 64 and 65 have beenassembled in the opening of the cutter, the ends of the extensions 66being welded to the outer bearing part at the shoulders 76. The openings74 in the outer bearing parts are suiiciently large in diameter topermit the ends of the extensions 66 to be welded to the outer bearingpart as at 77. As the bearings 54 are supported by the pins 55 and arearranged in the recesses 36 so that they are not subjected to any severepressures or strains, they may be treated so as to have maximum orefficient wear resisting qualities. Projecting lugs 78 are provided onthe outer end 73 of each bearing part 65. The lugs 78 are shaped andproportioned to fit the slots 40 in the outer walls of the wings 33. Inaccordance with the invention, the lugs 78 are flat sided and aresuilicientlylong to extend intothe counter bores 43.

The pins or bolts 55 are provided to detachably lock or secure theassemblies of the cutters 53 land bearings 54 in the recesses 36 of thebit head. The bolts 55 are adapted to be passed inwardly through theouter bores 42, the openings in the bearing 54, and iinally into theinner bores 41. 'Ihe body portions of the bolts 55 are proportioned toslidably t the openings 70 in the inner bearing parts 64. Heads 79 areprovided on the outer ends of the bolts 55 and are adapted to seat inthe outer counter bores 43. A notch 80 is provided in each bolt head 79to receive or cooperate with the lug 78 on the outer end of a bearing.The cooperation of the lugs 78 with the notches 80 holds the bolts 55against rotation. The outer ends of the bolt heads 79 may be bevelled orcut away to be ilush with the outer sides of the wings 33. Nuts 81 arethreaded on the reduced inner ends of the bolts 55 and seat or fit inthe sockets 71 in the inner ends of the bearings. The nuts 81. seat inthe bores 41 and may have enlargements or projecting flanges 82 on theirouter ends extending into the inner counter bores 44. After the bolts 55have been passed through the bores 42 and bearings 54, the nuts 81 maybe threaded onto their inner ends to lock the assembly in position. Theextreme inner end portions of the bolts 55 may then be peened topreventl loss or displacement of the nuts 81. If desired or foundpractical, the heads 79 of the bolts may be shaped and proportioned tofit the counter bores 43 or both the bores 42 and the counter bores 43,and in a like manner the nuts 81 may be shaped to fit the counter bores44 or both the bores 41 and the counter bores 44. In the simple form ofthe invention illustrated in the drawings, the bodies of the bolts seatin the bores 42 and the nuts 81 seat in the bores 41 to retain thecutter assembly in position.

It will be apparent how the pins 55 effectively and dependably connector secure the assemblies of the cutters 53 and the bearings 54 to theshoe 28 in their proper positions in the recesses 36. The cooperation ofthe bolts 55 with the bores 42 and the cooperation of the reducedcylindrical portions of the nuts 81 with the inner bores 41 hold theassemblies against downward displacement from the bit head. The lugs 69and 78 in cooperating with the slots,40 positively prevent turning ofthe bearings 54 and ald in transmitting upward forces from the bearingsto the shoe 28. The bolt heads '79 and the nuts 81 cooperatewith theends of the counterbores 42 and 41 respectively so that the walls of theshoe 28 at the inner and outlet ends of the recesses are rigidlyconnected together. The cooperation of the oppositely facing shoulders67 and 72 with the shoulders 6l and 63 of the cutters provide for thetransmission of end thrusts from the cutters to the bearings while theengagement of the ends of the bearings with the end walls of therecesses 36 insures the dependable transmission of end thrusts directlyfrom a bearing to the shoe 28. The threadedly connected bolts 55 andnuts 81 act to effectively connect or tie together the portions of theshoe 28 at the inner and outer ends of the recesses 36.

Each of the inner cutter assemblies 14 includes a cutter 83, bearings 84and bolts 85. The cutters 83 are rotatable about upwardly and inwardlyinclined axes and may be frustro-conical, so that the cutting parts attheir lower ends are substantially horizontal. When mounted in therecesses 37, the cutters 83 project from the lower ends of the recessesto engage the formation at the bottom of the well bore and projectinwardly to trim the core as it passes upwardly into the shoe opening31. The cutters 83 are provided with central longitudinal openingshaving inner sockets 87 and outer enlargements or sockets 88. The bottomof each inner socket 87 forms an inwardly facing shoulder 89, while thebottom of each outer socket 88 forms an outwardly facing shoulder 90.The shoulders 89 and 90 may be tapered inwardly or toward one another asillustrated throughout the drawings. The bearings 84 may be similar tothe bearings 54 described above, each including two parts integrallyconnected or joined by welding 91. The bearings 84 thus constituteone-piece members and have oppositely facing shoulders for cooperatingwith the cutter shoulders 89 and 90. Where the inner cutters 83 arerotatable about upwardly and inwardly inclined axes, their innershoulders 89 are of comparatively large diameter and are operable tocooperate with complementary shoulders 92 on the bearings 83. The outerinternal shoulders 90 of the cutters may be smaller in diameter tocooperate with opposing shoulders 93 on the bearings 84.

The bolts 85 are passed through the openings in the bearings 84 andtheir inner end portions cooperate with the bores 49. Heads 95 areprovided on the inner ends of the bolts 85 to seat in the counter bores51. Lugs 96 are provided on the inner ends of the bolts 85 to seat inthe counter bores 51. Lugs 96 are provided on the inner ends of thebearings 84 to cooperate with the slots 4'7 and with notches in theedges o! the bolt head 95. Lugs 97 are provided on the outer ends of thebearings 84 to cooperate with the slots 47 at the outer walls of therecesses 37. Nuts 98 are screw-threaded on to the outer end portions ofthe bolts 85 and iit the counter sink in the outer ends of the bearings84. The nuts fit or seat in the bores 48. Enlargements on the nuts 85seat in the outer counter bores 50. The outer ends of the bolts 85 maybe peened to prevent displacement or loosening of the nuts 98. Themanner of assembling and mounting the inner cutter assemblies 14 isidentical with that of the outer cutter assemblies 13.

The invention provides novel and effective means for flushing or washingthe cutters 53 and 83 of the two sets of cutter assemblies. Anenlargement or annular recess 100 is provided in the wall of the subopening 20 at the lower end of the socket 22. Longitudinal fluidpassages 101 extend downwardly through the walls of the bit head sub 19from the recess 100 to the lower end of the sub. An annular recess 102is provided in the lower end of the sub 19 and is in communication withthe ends of the passages 101. The shoulder 30 closes the lower end ofthe recess 102 so that the recess 102 forms an annular space at theconnection between the shoe 29 and the sub 19. Passages 103 are providedin the shoe 28 and extend downwardly from the shoulder 30 where theycommunicate with the space 102 to the upper ends of the recesses 36 and27. It will be apparent how the circulation uid owing downwardly throughthe annular space 24 is carried through the fluid passages in the sub 19and bit head 28 to discharge from the lower ends of the passages 103 andeifectively wash and ilush the cutters 53 and 83. ,f

The core drill may include a suitable core catching means for holding orretaining the core in the inner barrel 11. It is to be understood thatany suitable form of core catcher may be employed in connection with theinvention. In Fig. 1 of the drawings we have shown a more or lesstypical core catcher including a ring slidable longitudinally in theopening 20 of the sub 19. Upwardly projecting spring ngers 111 areprovided in the ring 110 to aid in supporting the core in the barrel 11.Spring fingers 112 project downwardly from the ring 110 and carry attheir lower ends toothed slips 113. The intermediate portion of the shoeopening 31 is provided with downwardly and inwardly tapering walls andthe slips 113 are adapted to cooperate with these walls to be forcedinwardly into gripping engagement with the core when the tool is movedupwardly with respect to the core.

Fig. 9 of the drawings illustrates the cutter mounting means provided bythe present invention rotatably supporting a cylindrical cutter 120 in arecess 121 in the lower end of a bit head shoe 122. The inner and outerwalls of the recess 121 are inclined downwardly and inwardly andvertical radial slots 123 intersect the lower end portions of therecesses. Bores and counterbores are provided at the slots 123corresponding in arrangement and purpose to the bores 48 and 49 and thecounter bores described above. These bores are coaxial, and their axesare inclined upwardly and inwardly. The cutter assembly includes, inaddition to the cutter 120, a bearing 125 and a bolt 126. The bearing125 may be substantially identical with the bearing 84 described 'above,being formed of two integrally joined parts. The bearing 125 is providedintermediate its ends with spaced oppositely facing shoulders 128 forcooperating with complementary shoulders in the cutter opening. Theopposite ends of the bearing125 seat against the opposite end walls ofthe recess 121 and lugs 96l and 88B are provided on the inner and outerends of the bearing to cooperate with the slot 123 to hold the bearingagainst rotation. The bolt 126 extends through the bearing 125 and isprovided at its outer end with a head 130 cooperating with a counterbore and engaged by the lug 96a so that the bolt 126 is held againstrotation. A nut 131 ls threaded on the inner end of the bolt 126 andiscounter sunk in the outer end of the bearing 125. A flange 132 isprovided on the nut 121 to extend into a counter bore 133. Theprojecting end of the bolt 126 may be peened over to prevent loss of thenut 121.

Fig. 10 of the drawings illustrates a frustoconical cutter 140 rotatablymounted in a recess 141 in a bit head shoe 142. The cutter 140corresponds generally to one of the cutters 83 described above, however,it is positioned in the downwardly and inwardly sloping recess 141 tohave its small or reduced end at the lower end of the core passingopening 143 of the shoe. When the cutter 140 is mounted in this manner,its cutting teeth 144 project from the lower end of the shoe 142 and areinclined upwardly and inwardly where they engage the formation at thebottom of the well bore. The inner ends of the cutting teeth 144 may bebevelled so that they effectively trim or shape the core adjacent thelower end of the shoe. The cutter 140 may be mounted in the same manneras one of the cutters 83 described above. The bearing 146 rotatablysupporting the cutter 140 has two oppositely facing shouldersintermediate its ends, the outer of which is of the greatest diameter.Complementary opposite facing shoulders are provided in the opening ofthe cutter 140 to c0- operate with the bearing shoulders. A bolt 150passes through the bearing and a nut 151 is threaded on the outer end ofthe bolt. The bolt 150 may be identical with the bolt 55 describedabove, and operates in the samemanner to removably lock the cutterassembly in the recess 141.

It is believed that the utility and practicability of the Well toolprovided by the present invention will be readily apparent from theforegoing description. It is to be understood that the shoe 28 of thebit head is a simple integral member that is inexpensive of manufactureand of sturdy construction. The provision of the recess 102 in the lowerend of the bit head sub 19 insures the proper delivery of circulationfluid to the discharge passages 103. 'I'he removable or detachablecutter assemblies provided by the present invention are such that theymay be easily and quickly replaced at the well drilling rig. Theone-piece bearing rotatably carrying the cutter may be easily passedupwardly into the recess in the lower end of the shoe 28. The lockinglugs on the opposite ends of the bearing properly locks or positions thebore and acts to positively prevent rotation of the bearing. The boltcooperates with the bore at the outer end of the cutter carrying recessand the nut on the bolt cooperates with the other counter bore toprevent displacement of the cutter assembly from the lower end of thebit head. The cooperation ofthe lug with the notch in the bolt headeffectively holds the bolt against turning. The opposite ends of thebearing may seat against the oppositeend walls of the recess in the bithead, so that the bearing has no tendency for longitudinal movement. Ina like manner, the oppositely facing shoulders on the interior of thecutter cooperate with the two shoulders on the bearing to positivelyprevent longitudinal movement of the cutter on the bearing. 'I'hecooperation of the shoulders on the bearing and cutter insures thetransmission of all the end thrusts directly from the cutter to thebearing and prevents engagement of the cutter with the walls of therecess in the sh. The slots, bores and counter bores in the shoe insurethe proper positioning of the cutter assembly in the recess of the bithead. The nut may be easily removed from the bolt so that the bolt maybe disengaged from the bit head and the bearing and the assembly of thecutter and bearing removed from the recess. The cutter assembly or meansfor detachably mounting the cutter on the bit head is simple andinexpensive of manufacture, and is positive and dependable in operation,as the parts cannot become loosened or displaced.

Having described only typical preferred forms of our invention, we donot wish to limit ourselves to the specific details set forth, but wishto reserve to ourselves any changes or variations that may appear tothose skilled in the art or fall within the scope of the followingclaims.

Having described our invention, we claim:

1. In a well tool, a body having a recess in its lower end, there beinga slot in the lower end of the body intersecting the recess, and a, borein the walls of the slot intersecting the recess, a bearing extendingthrough the recess, parts projecting from opposite ends of the bearingengaging the slot to hold the bearing against rotation, and a removablebolt extending through the bore and carrying the bearing, one of saidparts engaging the bolt to hold it against rotation.

2. A cutter assembly for a well tool including a cutter having anopening, and a bearing for rotatably carrying the cutter comprising twointegrally joined parts, one part extending into each end of the cutteropening, each of said parts having portions of different diametersjoined by an inwardly facing shoulder, there being oppositely facingshoulders on the walls of the cutter opening for cooperating with theshoulders of the bearing.

3. A cutter assembly for a well tool including, a cutter having anopening enlarged at its ends to form outwardly facing inclinedshoulders, and a bearing for .rotatably carrying the cutter comprising,two parts having aligned openings to receive a mounting member, one partextending into each end of the opening in the cutter, the said bearingparts having integrally joined -telescoping portions and each having aninclined shoulder for engaging a shoulder in the opening in the cutter.

4. In a well tool, a body having a recess, a bearing extending throughthe recess and comprising two sections one having a tubular part and theother having an opening through it receiving the tubular part, the innerend portion of said tubular part being integrally secured in the openingin said other part, shoulders on the sections facing one another, acutter rotatable on thebearing and having shoulders cooperating with theshoulders on the bearing, means holding the bearing against rotation,and a bolt carrying the bearing and tying together the portions of thebody at the opposite ends of the recess.

5. In a well drill a cutter bearing including two sections, one havingan opening through it to receive a mounting pin and having a largebearing part at one end and a reduced bearing part projecting therefrom,the other section having a bore receiving the projecting end portion ofthe reduced part of the rst mentioned section, said end portion of thesaid reduced part being integrally connected with said other section,the sections having opposed inclined cutter retaining shoulders.

6. In a well drill a cutter bearing including two sections, one havingan opening through it to receive a mounting pin and having a largebearing part at one end and a reduced bearing part projecting therefrom,the other section having a bearing part substantially larger in diameterthan any bearing part of the rst mentioned section and having a borereceiving the projecting end portion of the reduced part of the rstmentioned section, said end portion of the said reduced part beingintegrally connected with said other section. the sections havingopposed cutter retaining shoulders.

7. In a well tool, a body having a recess in its lower end, there beinga slot in the lower end of the body intersecting the recess, and a borein the walls of the slot intersecting the recess, a bearing extendingthrough the recess, a part on the bearing engaging the slot to hold thebearing against rotation, a removable bolt `extending through the boreand carrying the bearing, and a lug and notch connection between thesaid part and bolt to hold the bolt against rotation.

JOHN H. HOWARD. ALFRED C. CATLAND.

